Fourier-transform interferometer using meta surface

ABSTRACT

A Fourier-transform interferometer includes a phase change plate including a reflective layer configured to reflect a first light that is incident, and a meta surface configured to locally and differently change a phase of the first light that is reflected. The Fourier-transform interferometer further includes a photodetector configured to detect a second light, and a transflective mirror and a mirror configured to transmit a first part of a third light that is incident, to the phase change plate, transmit a remaining part of the third light, to the photodetector, and transmit the first light of which the phase is locally and differently changed, to the photodetector. The photodetector is further configured to detect an interference pattern between the remaining part of the third light and the first light of which the phase is locally and differently changed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2017-0155810, filed on Nov. 21, 2017, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

Apparatuses consistent with embodiments relate to a Fourier transforminterferometer and, more particularly, to a Fourier transforminterferometer using a meta surface.

2. Description of the Related Art

An interferometer is a device that divides light from the same lightsource into two paths, allows the light to travel on the differentpaths, and then observes an interference phenomenon caused by allowingthe light traveling on the different paths to meet again. Variousmeasurements such as a distance, an angle, a temperature change, anobject displacement, an object deformation, a refractive index ofmedium, a biological sample analysis, etc. may be possible by using theinterferometer. Also, a spectrum distribution of incident light may beanalyzed through a Fourier analysis on an interference pattern.

Recently, because an interest in convergence technology has increased,various measurements, a bio-analysis, and image editing have beenattempted by using a small electronic device, such as a smart phone,equipped with the interferometer. However, because the conventionalFourier transform interferometer has a structure to move a mirror tomomentarily change the phase of the reflected light, it is difficult tomanufacture the Fourier transform interferometer in a small chip form.

SUMMARY

According to embodiments, a Fourier-transform interferometer includes aphase change plate including a reflective layer configured to reflect afirst light that is incident, and a meta surface configured to locallyand differently change a phase of the first light that is reflected. TheFourier-transform interferometer further includes a photodetectorconfigured to detect a second light, and a transflective mirror and amirror configured to transmit a first part of a third light that isincident, to the phase change plate, transmit a remaining part of thethird light, to the photodetector, and transmit the first light of whichthe phase is locally and differently changed, to the photodetector. Thephotodetector is further configured to detect an interference patternbetween the remaining part of the third light and the first light ofwhich the phase is locally and differently changed.

The phase change plate may further include a substrate, the reflectivelayer may be disposed on the substrate, the meta surface may be disposedon the reflective layer, and the meta surface may include a plurality ofphase change elements having different diameters.

The plurality of phase change elements may have columnar shapesvertically protruding from the reflective layer.

The phase change plate may include a first meta region and a second metaregion that differently change the phase of the first light that isreflected.

The phase change plate may include first phase change elements disposedin the first meta region, and second phase change elements disposed inthe second meta region.

Each of the first phase change elements may have a first diameter, andeach of the second phase change elements may have a second diameterdifferent from the first diameter.

Each of the different diameters of the plurality of phase changeelements may be less than a wavelength of light to be analyzed.

Each of refractive indices of the plurality of phase change elements maybe higher than a refractive index of the substrate.

The photodetector may be disposed toward a first surface of thetransflective mirror, the mirror and the phase change plate may bedisposed toward a second surface opposite to the first surface of thetransflective mirror, and the transflective mirror may be disposed suchthat the third light is incident on the first surface of thetransflective mirror.

The transflective mirror may be disposed opposite an upper surface ofthe phase change plate, and the mirror and the photodetector may berespectively disposed on both sides of the transflective mirror.

The Fourier-transform interferometer may further include a substrate,and the transflective mirror, the phase change plate, the mirror, andthe photodetector may be disposed on the substrate.

The Fourier-transform interferometer may further include a light sourceconfigured to irradiate a fourth light toward a sample.

According to embodiments, a Fourier-transform interferometer includes atransflective mirror configured to transmit a first part of a firstlight that is incident, and reflect a remaining part of the first light,a phase change plate disposed opposite to the transflective mirror andincluding a meta surface configured to locally and differently change aphase of a second light that is incident, and a photodetector configuredto detect an interference pattern between a third light that istransmitted through the phase change plate.

The phase change plate may further include a transflective substrateconfigured to transmit a second part of the second light, and reflect athird part of the second light, the meta surface may be disposed on thesubstrate, and the meta surface may include a plurality of phase changeelements having different diameters.

The plurality of phase change elements may have columnar shapesvertically protruding from the substrate.

The phase change plate may include a first meta region and a second metaregion that differently change the phase of the third part of the secondlight that is reflected.

The phase change plate may include first phase change elements disposedin the first meta region, and second phase change elements disposed inthe second meta region.

Each of the first phase change elements may have a first diameter, andeach of the second phase change elements may have a second diameterdifferent from the first diameter.

Each of the different diameters of the plurality of phase changeelements may be less than a wavelength of light to be analyzed.

Each of refractive indices of the plurality of phase change elements maybe higher than a refractive index of the substrate.

The photodetector, the phase change plate, and the transflective mirrormay be sequentially arranged in a vertical direction.

The Fourier-transform interferometer may further include a substrate,and the transflective mirror, the phase change plate, and thephotodetector may be sequentially arranged in a lateral direction on thesubstrate.

The Fourier-transform interferometer may further include a light sourceconfigured to irradiate a fourth light toward a sample.

According to embodiments, a Fourier-transform interferometer includes amirror, a phase change plate, a photodetector, and a transflectivemirror configured to transmit a first part of a first light that isincident, to the phase change plate, and reflect a second part remainingof the first light, to the photodetector. The phase change plate isconfigured to reflect the first part of the first light that istransmitted, and change a phase of the first part of the first lightthat is reflected, to generate a second light, the transflective mirroris further configured to reflect a third part of the second light thatis generated, to the mirror, the mirror is configured to reflect thethird part of the second light reflected by the transflective mirror,the transflective mirror is further configured to transmit a fourth partof the third part of the second light reflected by the mirror, and thephotodetector is configured to detect an interference pattern betweenthe second part remaining of the first light and the fourth part of thethird part of the second light that is transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 shows a schematic configuration of a Fourier transforminterferometer according to an embodiment;

FIG. 2 shows a schematic configuration of a Fourier transforminterferometer according to another embodiment;

FIG. 3 shows a schematic configuration of a Fourier transforminterferometer according to another embodiment;

FIG. 4 shows a schematic configuration of a Fourier transforminterferometer according to another embodiment;

FIG. 5 is a perspective view showing a schematic configuration of aphase change plate of the Fourier transform interferometer shown in FIG.1;

FIG. 6 is a cross-sectional view showing a diameter and a pitch of eachof phase change elements of the phase change plate in the Fouriertransform interferometer shown in FIG. 1;

FIG. 7 is a graph exemplarily showing a phase change according to adiameter and a pitch of each of phase change elements;

FIG. 8 is a plan view showing a schematic configuration of the phasechange plate of the Fourier transform interferometer shown in FIG. 1;

FIG. 9 is a perspective view showing a vertical-type structure of theFourier transform interferometer shown in FIG. 1;

FIG. 10 is a perspective view showing a lateral-type structure of theFourier transform interferometer shown in FIG. 1;

FIG. 11 shows a schematic configuration of a Fourier transforminterferometer according to another embodiment;

FIG. 12 shows a schematic configuration of a Fourier transforminterferometer according to another embodiment;

FIG. 13 is a perspective view showing a schematic configuration of aphase change plate of the Fourier transform interferometer shown in FIG.11;

FIG. 14 is a perspective view showing a vertical-type structure of theFourier transform interferometer shown in FIG. 11; and

FIG. 15 is a perspective view showing a lateral-type structure of theFourier transform interferometer shown in FIG. 11.

DETAILED DESCRIPTION

Hereinafter, with reference to the accompanying drawings, a Fouriertransform interferometer using a meta surface will be described indetail. Like reference numerals refer to like elements throughout, andin the drawings, sizes of elements may be exaggerated for clarity andconvenience of explanation. The embodiments described below are anexample, and various modifications may be possible from the embodiments.In a layer structure described below, an expression “above” or “on” mayinclude not only “immediately above/below/left/right in a contactmanner” but also “above/below/left/right in a non-contact manner.”

FIG. 1 shows a schematic configuration of a Fourier transforminterferometer 100 according to an embodiment. Referring to FIG. 1, theFourier transform interferometer 100 according to an embodiment mayinclude a transflective mirror 111 that transmits a part of an incidentlight and reflects a remaining part of the incident light, a phasechange plate 120 that reflects the incident light and locally changes aphase of the reflected light differently, a mirror 112 that reflects thelight reflected from the phase change plate 120 toward the transflectivemirror 111, and a photodetector 130 that detects light.

For example, the photodetector 130 may be disposed toward a firstsurface 111 a of the transflective mirror 111, and the mirror 112 andthe phase change plate 120 may be disposed toward a second surface 111b, which is an opposite surface to the first surface 111 a of thetransflective mirror 111. The transflective mirror 111 may be disposedwhere an incident light to be analyzed is incident on the first surface111 a of the transflective mirror 111. Also, the photodetector 130 andthe mirror 112 may be disposed on both sides of the transflective mirror111.

In this configuration, a part of the incident light that is incident onthe first surface 111 a of the transflective mirror 111 and is to beanalyzed transmits through the transflective mirror 111, and a remainingpart of the incident light to be analyzed is reflected by thetransflective mirror 111. A part of the incident light transmittedthrough the transflective mirror 111 is reflected by the phase changeplate 120. The phase change plate 120 locally and differently changesthe phase of the reflected light. Therefore, the light reflected by thephase change plate 120 has various phases according to a cross-sectionalarea of a beam. Then, a part of the light reflected from the phasechange plate 120 is reflected by the second surface 111 b of thetransflective mirror 111 and is incident on the mirror 112. A part ofthe light reflected by the mirror 112 transmits through thetransflective mirror 111 and is incident on the photodetector 130.

The light reflected from the first surface 111 a of the transflectivemirror 111 is also incident on the photodetector 130. Therefore, thelight not incident on the phase change plate 120 and the light reflectedfrom the phase change plate 120 are incident on the photodetector 130.As a result, an interference pattern is formed between the light notincident on the phase change plate 120 and the light reflected from thephase change plate 120 in the incident light. Therefore, thephotodetector 130 may detect the interference pattern between the lightnot incident on the phase change plate 120 and the light reflected fromthe phase change plate 120 in the incident light. Then, a spectrumdistribution of the incident light may be analyzed by using a Fourieranalysis method using the interference patterns detected by thephotodetector 130.

In FIG. 1, the photodetector 130 and the mirror 112 are disposed onopposite sides of the transflective mirror 111, and the phase changeplate 120 is disposed toward a direction in which the incident light isincident on the transflective mirror 111. However, embodiments are notnecessarily limited thereto.

FIG. 2 shows a schematic configuration of the Fourier transforminterferometer 100 according to another embodiment. Compared with FIG.1, positions of the phase change plate 120 and the mirror 112 areexchanged in FIG. 2. Therefore, the photodetector 130 and the phasechange plate 120 are disposed on opposite sides of the transflectivemirror 111, and the mirror 112 is disposed toward a direction in whichthe incident light is incident on the transflective mirror 111.

In this configuration, a part of an incident light that is incident onthe first surface 111 a of the transflective mirror 111 and is to beanalyzed transmits through the transflective mirror 111 and then isincident on the mirror 112, and a remaining part of the incident lightto be analyzed is reflected by the first surface 111 a of thetransflective mirror 111 and is incident on the photodetector 130. Thelight transmitted through the transflective mirror 111 is reflected bythe mirror 112 and is incident on the second surface 111 b of thetransflective mirror 111. A part of the light incident on the secondsurface 111 b of the transflective mirror 111 is reflected by the secondsurface 111 b of the transflective mirror 111 and is incident on thephase change plate 120. The phase change plate 120 reflects the incidentlight and locally and differently changes a phase of the reflectedlight. Then, a part of the light reflected by the phase change plate 120transmits through the transflective mirror 111 and is incident on thephotodetector 130.

Also, in FIG. 1, the photodetector 130 is disposed toward the firstsurface 111 a of the transflective mirror 111 and the mirror 112 and thephase change plate 120 are disposed toward the second surface 111 b.However, embodiments are not necessarily limited thereto.

FIG. 3 shows a schematic configuration of the Fourier transforminterferometer 100 according to another embodiment. Compared with FIG.1, positions of the photodetector 130 and the mirror 112 are exchangedin FIG. 3. Therefore, the mirror 112 may be disposed toward the firstsurface 111 a of the transflective mirror 111, and the photodetector 130and the phase change plate 120 may be disposed toward the second surface111 b of the transflective mirror 111.

In this configuration, a part of the incident light that is incident onthe first surface 111 a of the transflective mirror 111 and is to beanalyzed transmits through the transflective mirror 111 and is incidenton the phase change plate 120, and a remaining part of the incidentlight to be analyzed is reflected by the first surface 111 a of thetransflective mirror 111 and is incident on the mirror 112. A part ofthe light reflected by the mirror 112 transmits through thetransflective mirror 111 and is incident on the photodetector 130.Further, the phase change plate 120 reflecting the incident light andchanges a phase of the reflected light locally and differently. Then, apart of the light reflected by the phase change plate 120 is reflectedby the second surface 111 b of the transflective mirror 111 and isincident on the photodetector 130.

As described above, various configurations may be possible to allow thelight not incident on the phase change plate 120 and the light reflectedfrom the phase change plate 120 to be incident on the photodetector 130of the incident light. Accordingly, the Fourier transform interferometer100 according to the present embodiment may have various arrangements ofthe transflective mirror 111 and the mirror 112 for transmitting a partof the incident light to the phase change plate 120, transmitting aremaining part of the incident light to the photodetector 130, andtransmitting the light reflected from the phase change plate 120 in theincident light to the photodetector 130.

The incident light that is incident on the first surface 111 a of thetransflective mirror 111, which may be light to be analyzed, may belight directly from an external test target light source such as a laseror may be light reflected, transmitted, or scattered from an externalsample or subject. When the Fourier transform interferometer 100 is usedfor analyzing a sample, the Fourier transform interferometer 100 mayfurther include a light source.

FIG. 4 shows a schematic configuration of the Fourier transforminterferometer 100 according to another embodiment. Referring to FIG. 4,the Fourier transform interferometer 100 may further include a lightsource 110 for irradiating a sample S with light. In this case, thesample S, the light source 110, and the transflective mirror 111 may bedisposed where light reflected, transmitted or scattered from the sampleS irradiated by the light source 110 is incident on the first surface111 a of the transflective mirror 111.

FIG. 5 is a perspective view showing a schematic configuration of thephase change plate 120 of the Fourier transform interferometer 100 shownin FIG. 1. Referring to FIG. 5, the phase change plate 120 for locallychanging a phase of reflected light may include a substrate 121, areflective layer 122 disposed on the substrate 121, and a meta-surface123 disposed on the reflective layer 122 and locally and differentlychanging the phase of the reflected light. The phase change plate 120may be disposed where the reflection layer 122 and the meta surface 123face the transflective mirror 111.

The meta surface 123 may include a plurality of phase change elements124 having a plurality of different diameters. For example, theplurality of phase change elements 124 may have columnar shapes thatprotrude vertically on the reflective layer 122. The phase changeelements 124 have cylindrical shapes in FIG. 5 but are not limitedthereto. For example, the phase change elements 124 may have ellipticalcolumn shapes or rectangular column shapes wherein the phase changeplate 120 has a polarization-dependent characteristic.

The substrate 121 may be formed of glass or plastic material in the formof a flat plate. The phase change elements 124 may be formed of amaterial having a higher refractive index than that of the substrate121. For example, the phase change elements 124 may be formed of amaterial having a high refractive index selected from the groupconsisting of germanium (Ge), amorphous silicon (a-Si), polycrystallinesilicon (p-Si), crystalline silicon (c-Si), group III-V compound, SiNx,SiO₂, TiO, TiO₂, TiO₃, GaP, Al₂O₃, HfO₂, and the like. A refractiveindex of the phase change element 124 may be greater than 3.5 at, forexample, a visible light wavelength. Alternatively, the phase changeelements 124 may be formed of a metallic material. These phase changeelements 124 may be easily formed using a general semiconductorpatterning process. For example, after depositing material layers of thephase change elements 124 on the reflective layer 122, the phase changeelements 124 may be formed simply by patterning the phase change elementmaterial layers using a photolithography process and an etch process.Therefore, a complicated processing operation is not required to formthe phase change plate 120.

Pitches between the phase change elements 124 and diameters of the phasechange elements 124 may be much less than a wavelength of light to beanalyzed. Then, a phase may be delayed because the incident light passesthrough the phase change elements 124 of the high refractive index, andthus a phase of reflected light by the phase change plate 120 isdifferent from the phase of the incident light. A phase change degreemay vary according to parameters such as an arrangement, diameters,pitches, cross-sectional shapes, heights, and refractive indices of thephase change elements 124. To simplify a manufacturing process of thephase change plate 120, the plurality of phase change elements 124 maybe simply two-dimensionally arranged, and the phase of the reflectedlight may be adjusted only by the pitch and diameter of each of thephase change elements 124. For example, the parameters such as thearrangement of the phase change elements 124, the cross-sectionalshapes, the heights, and the like may be the same, and the phase of thereflected light may be adjusted only by the pitch and the diameter.

FIG. 6 is a cross-sectional view showing a diameter d and a pitch P ofeach of the phase change elements 124 of the phase change plate 120 inthe Fourier transform interferometer 100 shown in FIG. 1. FIG. 7 is agraph exemplarily showing a phase change according to the diameter andthe pitch of each of the phase change elements 124. Referring to FIG. 6,the pitch P is an arrangement period of the phase change elements 124,and is a distance from a center of one of the phase change elements 124to a center of another one of the phase change elements 124 adjacentthereto. In FIG. 7, the horizontal axis represents a ratio (d/p) betweenthe pitch and the diameter, and the vertical axis represents areflectance and a phase. Referring to FIG. 7, it may be seen that theratio (d/p) between the pitch and the diameter increases with respect toan incident light of 600 nm and 700 nm, and that the phase changegradually increases. Also, it may be seen that the reflectance is almostconstant regardless of the ratio (d/p) between the pitch and thediameter. Therefore, the phase of the reflected light may be adjusted byadjusting the ratio (d/p) between the pitch and the diameter.

The meta surface 123 may include a plurality of meta regions fordifferently changing the phase of the reflected light.

FIG. 8 is a plan view showing a schematic configuration of the phasechange plate 120 of the Fourier transform interferometer 100 shown inFIG. 1. Referring to FIG. 8, the meta surface 123 may include first tofourth meta regions 120 a, 120 b, 120 c, and 120 d. Although only thefour meta regions 120 a, 120 b, 120 c, and 120 d are illustrated in FIG.8, there may actually be a greater number of meta regions. The first tofourth meta regions 120 a, 120 b, 120 c, and 120 d may be configured tochange a phase of a reflected light differently. To this end, aplurality of first to fourth phase change elements 124 a, 124 b, 124 c,and 124 d that are different from each other may be respectivelyarranged in the first to fourth meta regions 120 a, 120 b, 120 c, and120 d. For example, the first to fourth phase change elements 124 a, 124b, 124 c, 124 d arranged in the same meta regions 120 a, 120 b, 120 c,and 120 d all have the same diameter and pitch, and the first to fourthphase change elements 124 a, 124 b, 124 c, and 124 d arranged in thedifferent first to fourth meta regions 120 a, 120 b, 120 c, and 120 dmay be configured to have different diameters and pitches.

Then, light reflected by the phase change plate 120 may have differentphases according to a local position in the phase change plate 120. Inother words, the phase of the reflected light changes locally accordingto the position on the phase change plate 120. For example, reflectedlight reflected on the first meta region 120 a of the phase change plate120 may have a first phase, reflected light reflected on the second metaregion 120 b of the phase change plate 120 may have a second phase, thesecond phase being different from the first phase, reflected lightreflected on the third meta region 120 c of the phase change plate 120may have a third phase, the third phase being different from the firstand second phases, and reflected light reflected on the fourth metaregion 120 d of the phase change plate 120 may have a fourth phase, thefourth phase being different from the first to third phases.

According to the embodiment described above, because the phase changeplate 120 locally changes the phase of the reflected light, a pluralityof different optical path differences may occur simultaneously betweenlight not incident on the phase change plate 120 in the incident lightand the light reflected from the phase change plate 120. As a result, alarge number of different interference patterns may occursimultaneously. Therefore, because the Fourier transform interferometer100 according to the present embodiment does not include a mechanicalstructure for moving a mirror to change the optical path differencesbetween the two lights incident on the photodetector 130, the Fouriertransform interferometer 100 may be manufactured in a small size. Forexample, the Fourier transform interferometer 100 according to thepresent embodiment may be manufactured in a chip form and applied to asmall electronic device such as a smart phone or a wearable device.Also, because a plurality of different interference patterns occursimultaneously, it is possible to analyze the incident light in realtime. Further, because the phase change plate 120 may be simplymanufactured by a patterning method using a photolithography process, acomplicated processing operation is not required. Therefore, themanufacturing cost of the Fourier transform interferometer 100 may bereduced.

The Fourier transform interferometer 100 having the configuration shownin FIGS. 1 to 4 may be implemented having a vertical-type structure or alateral-type structure.

FIG. 9 is a perspective view showing a vertical-type structure of theFourier transform interferometer 100 shown in FIG. 1, and FIG. 10 is aperspective view showing a lateral-type structure of the Fouriertransform interferometer 100 shown in FIG. 1.

Referring to FIG. 9, the phase change plate 120 may be disposed in abottom region of the Fourier transform interferometer 100, and thetransflective mirror 111 may face an upper surface of the phase changeplate 120 and be spaced apart from the phase change plate 120. Themirror 111 and the photodetector 130 may be respectively disposed onboth sides of the transflective mirror 111. An incident light may beincident on the transflective mirror 111 in a vertical direction fromthe top to the bottom. FIG. 9 exemplarily shows the configuration shownin FIG. 1. The configurations shown in FIG. 2 through FIG. 4 may beimplemented as the vertical-type structure shown in FIG. 9.

Also, referring to FIG. 10, the Fourier transform interferometer 100 mayfurther include a flat substrate 101. In this case, all of thetransflective mirror 111, the phase change plate 120, the mirror 112,and the photodetector 120 may be arranged on an upper surface of thesubstrate 101. In this case, the incident light may proceed in ahorizontal direction and may be incident on the transflective mirror111. FIG. 10 exemplarily shows the configuration shown in FIG. 1. Theconfigurations shown in FIG. 2 through FIG. 4 may be implemented as thevertical-type structure shown in FIG. 9.

The Fourier transform interferometer 100 described in FIGS. 1 to 10 is aMichelson interferometer in which the phase change plate 120 changes aphase of reflected light. However, the Fourier transform interferometer100 may be configured as Fabry-Perot interferometer in which a phasechange plate changes a phase of transmitted light.

FIG. 11 shows a schematic configuration of a Fourier transforminterferometer 200 according to another embodiment. Referring to FIG.11, the Fourier transform interferometer 200 may include a transflectivemirror 210 transmitting a part of an incident light and reflecting aremaining part of the incident light, a phase change plate 220 disposedopposite to the transflective mirror 210, and a photodetector 230disposed opposite the phase change plate 220. The photodetector 230 maybe disposed on the opposite side of the transflective mirror 210 withrespect to the phase change plate 220.

In the configuration of the Fourier transform interferometer 200, a partof the incident light incident on the transflective mirror 210 passesthrough the transflective mirror 210 and is incident on the phase changeplate 220. A part of light incident on the phase change plate 220 isreflected by the transflective mirror 210 and a remaining part of thelight transmits through the phase change plate 220 and is incident onthe photodetector 230. A part of the light reflected by the phase changeplate 220 and incident on the transflective mirror 210 may be reflectedagain and then may transmit through the phase change plate 220 and beincident on the photodetector 230. In the present embodiment, the phasechange plate 220 may have a meta surface that locally changes a phase ofthe transmitted light. Therefore, the photodetector 230 may detect aninterference pattern between the light transmitted through the phasechange plate 220. For example, the photodetector 230 may detect aninterference pattern between light transmitting through the phase changeplate 220 once and light reciprocating one or more times between thephase change plate 220 and the transflective mirror 210. Then, aspectrum distribution of the incident light may be analyzed by a Fourieranalysis method using the interference patterns detected by thephotodetector 230.

An incident light incident on the transflective mirror 210 from theoutside, which is light to be analyzed, may be light directly from anexternal test target light source such as a laser or reflected,transmitted or scattered from an external sample or subject. When theFourier transform interferometer 200 is used for analyzing a sample, theFourier transform interferometer 200 may further include a light source.

FIG. 12 shows a schematic configuration of the Fourier transforminterferometer 200 according to another embodiment. Referring to FIG.12, the Fourier transform interferometer 200 may further include thelight source 110 for irradiating the sample S with light. In this case,the sample S, the light source 110, and the transflective mirror 210 maybe arranged where light reflected, transmitted or scattered from thesample S irradiated by the light source 110 may be incident on thetransflective mirror 210.

FIG. 13 is a perspective view showing a schematic configuration of thephase change plate 220 of the Fourier transform interferometer 200 shownin FIG. 11. Referring to FIG. 13, the phase change plate 220 for locallyand differently changing a phase of a transmitted light may include thesubstrate 121 and the meta surface 123 disposed on the substrate 121 andlocally and differently changing a phase of a reflected light. Asdescribed with reference to FIG. 8, the meta surface 123 may include aplurality of meta regions for differently changing the phase of thereflected light, and the phase change elements 124 having a plurality ofdifferent diameters may be arranged in the plurality of meta regions.Therefore, compared with the phase change plate 120 of FIG. 5, the phasechange plate 220 shown in FIG. 13 may have the same configuration asthat of the phase change plate 120 shown in FIG. 5 except that the phasechange plate 220 shown in FIG. 13 does not include the reflective layer122.

The substrate 121 of the phase change plate 220 may be formed of amaterial having transparency with the light to be analyzed. For example,the substrate 121 may be formed of glass or a transparent plasticmaterial. Instead, the substrate 121 may have transflectivity to reflecta part of the incident light to the transflective mirror 210.

The Fourier transform interferometer 200 having the configuration shownin FIGS. 11 and 12 described above may also be implemented having avertical-type structure or a lateral-type structure.

FIG. 14 is a perspective view showing a vertical-type structure of theFourier transform interferometer 200 shown in FIG. 11, and FIG. 15 is aperspective view showing a lateral-type structure of the Fouriertransform interferometer 200 shown in FIG. 11.

Referring to FIG. 14, the photodetector 230 may be disposed in a bottomregion of the Fourier transform interferometer 200 and the phase changeplate 220 may face an upper surface of the photodetector 230 and bespaced apart from the photodetector 230. The transflective mirror 210may face an upper surface of the phase change plate 220 and be spacedapart from the phase change plate 220. An incident light may travel in aperpendicular direction from the top to the bottom and be incident onthe transflective mirror 210.

Referring to FIG. 15, the Fourier transform interferometer 200 mayfurther include a flat substrate 201. The transflective mirror 210, thephase change plate 220, and the photodetector 230 may be sequentiallyarranged in a lateral direction on an upper surface of the substrate201. In this case, the incident light may travel in a horizontaldirection and be incident on the transflective mirror 210.

It may be understood that the Fourier-transform interferometer using ameta surface described herein may be considered in a descriptive senseonly and not for purposes of limitation. Descriptions of features oraspects within each embodiment may be considered as available for othersimilar features or aspects in other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. A Fourier-transform interferometer comprising: aphase change plate comprising: a reflective layer configured to reflecta first light that is incident; and a meta surface configured to locallyand differently change a phase of the first light that is reflected; aphotodetector configured to detect a second light; and a transflectivemirror and a mirror configured to: transmit a first part of a thirdlight that is incident, to the phase change plate; transmit a remainingpart of the third light, to the photodetector; and transmit the firstlight of which the phase is locally and differently changed, to thephotodetector, wherein the photodetector is further configured to detectan interference pattern between the remaining part of the third lightand the first light of which the phase is locally and differentlychanged.
 2. The Fourier-transform interferometer of claim 1, wherein thephase change plate further comprises a substrate, the reflective layeris disposed on the substrate, the meta surface is disposed on thereflective layer, and the meta surface comprises a plurality of phasechange elements having different diameters.
 3. The Fourier-transforminterferometer of claim 2, wherein the plurality of phase changeelements have columnar shapes vertically protruding from the reflectivelayer.
 4. The Fourier-transform interferometer of claim 2, wherein thephase change plate comprises a first meta region and a second metaregion that differently change the phase of the first light that isreflected.
 5. The Fourier-transform interferometer of claim 4, whereinthe phase change plate comprises first phase change elements disposed inthe first meta region, and second phase change elements disposed in thesecond meta region.
 6. The Fourier-transform interferometer of claim 5,wherein each of the first phase change elements has a first diameter,and each of the second phase change elements has a second diameterdifferent from the first diameter.
 7. The Fourier-transforminterferometer of claim 2, wherein each of the different diameters ofthe plurality of phase change elements is less than a wavelength oflight to be analyzed.
 8. The Fourier-transform interferometer of claim2, wherein each of refractive indices of the plurality of phase changeelements is higher than a refractive index of the substrate.
 9. TheFourier-transform interferometer of claim 1, wherein the photodetectoris disposed toward a first surface of the transflective mirror, themirror and the phase change plate are disposed toward a second surfaceopposite to the first surface of the transflective mirror, and thetransflective mirror is disposed such that the third light is incidenton the first surface of the transflective mirror.
 10. TheFourier-transform interferometer of claim 1, wherein the transflectivemirror is disposed opposite an upper surface of the phase change plate,and the mirror and the photodetector are respectively disposed on bothsides of the transflective mirror.
 11. The Fourier-transforminterferometer of claim 1, further comprising a substrate, wherein thetransflective mirror, the phase change plate, the mirror, and thephotodetector are disposed on the substrate.
 12. The Fourier-transforminterferometer of claim 1, further comprising a light source configuredto irradiate a fourth light toward a sample.
 13. A Fourier-transforminterferometer comprising: a transflective mirror configured to transmita first part of a first light that is incident, and reflect a remainingpart of the first light; a phase change plate disposed opposite to thetransflective mirror and comprising a meta surface configured to locallyand differently change a phase of a second light that is incident; and aphotodetector configured to detect an interference pattern between athird light that is transmitted through the phase change plate.
 14. TheFourier-transform interferometer of claim 13, wherein the phase changeplate further comprises a transflective substrate configured to transmita second part of the second light, and reflect a third part of thesecond light, the meta surface is disposed on the substrate, and themeta surface comprises a plurality of phase change elements havingdifferent diameters.
 15. The Fourier-transform interferometer of claim14, wherein the plurality of phase change elements have columnar shapesvertically protruding from the substrate.
 16. The Fourier-transforminterferometer of claim 14, wherein the phase change plate comprises afirst meta region and a second meta region that differently change thephase of the third part of the second light that is reflected.
 17. TheFourier-transform interferometer of claim 16, wherein the phase changeplate comprises first phase change elements disposed in the first metaregion, and second phase change elements disposed in the second metaregion.
 18. The Fourier-transform interferometer of claim 17, whereineach of the first phase change elements has a first diameter, and eachof the second phase change elements has a second diameter different fromthe first diameter.
 19. The Fourier-transform interferometer of claim14, wherein each of the different diameters of the plurality of phasechange elements is less than a wavelength of light to be analyzed. 20.The Fourier-transform interferometer of claim 14, wherein each ofrefractive indices of the plurality of phase change elements is higherthan a refractive index of the substrate.
 21. The Fourier-transforminterferometer of claim 13, wherein the photodetector, the phase changeplate, and the transflective mirror are sequentially arranged in avertical direction.
 22. The Fourier-transform interferometer of claim13, further comprising a substrate, wherein the transflective mirror,the phase change plate, and the photodetector are sequentially arrangedin a lateral direction on the substrate.
 23. The Fourier-transforminterferometer of claim 13, further comprising a light source configuredto irradiate a fourth light toward a sample.
 24. A Fourier-transforminterferometer comprising: a mirror; a phase change plate; aphotodetector; and a transflective mirror configured to transmit a firstpart of a first light that is incident, to the phase change plate, andreflect a second part remaining of the first light, to thephotodetector, wherein the phase change plate is configured to reflectthe first part of the first light that is transmitted, and change aphase of the first part of the first light that is reflected, togenerate a second light, the transflective mirror is further configuredto reflect a third part of the second light that is generated, to themirror, the mirror is configured to reflect the third part of the secondlight reflected by the transflective mirror, the transflective mirror isfurther configured to transmit a fourth part of the third part of thesecond light reflected by the mirror, and the photodetector isconfigured to detect an interference pattern between the second partremaining of the first light and the fourth part of the third part ofthe second light that is transmitted.